1. Field of the Invention
This invention relates to a device for setting a cassette, which houses therein a sheet-shaped image recording medium, such as X-ray photographic film or a stimulable phosphor sheet, at a predetermined setting position. This invention particularly relates to a cassette setting device adapted to the setting of a plurality of cassettes having different sizes.
2. Description of the Prior Art
X-ray photographic film has heretofore been known as a recording medium, on which a radiation image of an object, such as a human body, is recorded. Also, as a recording medium used for the same purposes, a sheet provided with a layer of a stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) has heretofore been known. Such stimulable phosphor sheets are disclosed in, for example, U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395. When certain kinds of phosphors are exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays, such as visible light, light is emitted by the phosphor in proportion to the amount of energy stored thereon during its exposure to the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
A radiation image of an object is recorded on a stimulable phosphor sheet by, for example, exposing the stimulable phosphor sheet to radiation, which has passed through the object. The stimulable phosphor sheet, on which the radiation image has been stored, is then scanned two-dimensionally with stimulating rays, such as a laser beam, which cause it to emit light in proportion to the amount of energy stored during exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected. In this manner, an electric image signal representing the radiation image can be obtained.
Ordinarily, the stimulable phosphor sheet or the X-ray photographic film described above is housed in a light-tight cassette or a light-tight magazine. Each cassette serves to house a single sheet-shaped image recording medium, such as a stimulable phosphor sheet, therein. In general, the cassette is constituted of a box member provided with an opening, through which a recording medium is to be fed into and out of the box member, at a portion, and a cover member, which is mounted on the box member via a swing axis approximately parallel to the sheet-shaped image recording medium having been housed in the box member and which opens and closes the opening by swinging around the swing axis.
When the cassette is used during an operation for recording a radiation image on the stimulable phosphor sheet, or the like, the cassette is located at a position for exposure to, for example, radiation having passed through an object. The stimulable phosphor sheet, or the like, which has been housed in the cassette, is exposed to radiation, and a radiation image is thereby recorded thereon.
When a cassette is loaded to, for example, an radiation image read-out apparatus for reading out a radiation image from an image recording medium, such as a stimulable phosphor sheet, on which the radiation image has been stored, it is necessary to set the cassette accurately at a predetermined position such that the image recording medium housed in the cassette may be automatically conveyed out of the cassette and such that the image recording medium, from which the radiation image has been read out, may be automatically returned into the cassette. In general, a device for setting the cassette in such a manner is constituted such that the positions of two side ends of the cassette may be adjusted from the exterior by a pair of guide members. The cassette is inserted into the cassette setting device such that one end of the cassette provided with an opening, through which the image recording medium is to be fed into and out of the cassette, (i.e., the end of the cassette which is normal to the two side ends thereof) may first enter the cassette setting device. The two side ends of the cassette are guided by the guide members, and the cassette is thereby set at the predetermined position.
In the past, a cassette was provided with a cover member having the same size as the entire area of the upper surface of the cassette. Recently, as disclosed in, for example, Japanese Unexamined Patent Publication No. 63(1988)-103231, a cassette has been proposed which is provided with a comparatively small cover member occupying a portion of the entire area of the upper surface of the cassette. In general, when the cassette provided with such a small cover member is loaded to a radiation image read-out apparatus, or the like, instead of the entire cassette being loaded into the radiation image read-out apparatus, or the like, only a portion of the cassette adjacent its one end, which is opened and closed by the cover member, is accommodated in the apparatus, and the portion of the cassette adjacent the other end thereof is projected out of the apparatus. Specifically, in such cases, the space in the radiation image read-out apparatus, or the like, for accommodating the cassette can be kept small, and therefore the size of the radiation image read-out apparatus, or the like, can be kept small.
The radiation image read-out apparatus, or the like, is often constituted such that a plurality of image recording media having different sizes may be processed therein. In such cases, various cassettes having different sizes are utilized. However, in cases where cassettes having different sizes are to be processed, the conventional cassette setting device is constituted so as to accommodate the entire cassette in the radiation image read-out apparatus, or the like. Specifically, the conventional cassette setting device is not constituted such that only a portion of the cassette adjacent its one end, which is opened and closed by the cover member, may be accommodated in the region inside of the radiation image read out apparatus, or the like.
The reasons for the above are that it becomes difficult to shield the region inside of the radiation image read-out apparatus, or the like, from external light. Specifically, when a cassette is loaded to the radiation image read-out apparatus, or the like, wherein various processes are carried out on an image recording medium, such as a stimulable phosphor sheet or X-ray photographic film, the apparatus must be shielded from external light such that no external light may enter the region inside of the apparatus. In cases where only a portion of a cassette adjacent its one end is accommodated in the region inside of the radiation image read-out apparatus, or the like, if cassettes having the same size are always processed, the light shielding can be effected without difficulty. However, in cases where cassettes having different sizes are to be processed, if a cassette having a comparatively small size is loaded to the radiation image read-out apparatus, or the like, external light will easily enter the region inside of the apparatus from spaces occurring on the two sides of the cassette.
As described above, for reasons of the light shielding, a cassette has heretofore been loaded to the radiation image read-out apparatus, or the like, such that the entire cassette may be accommodated in the apparatus. In such cases, the radiation image read-out apparatus, or the like, must be provided with the space for accommodating the entire cassette, and therefore the size of the apparatus cannot be kept small.